Start with the operating decision: CHA OCF40 does not have one universal NVIS or DX pattern. Band, height in wavelengths, horizontal versus inverted-V geometry, orientation, ground, and nearby structures reshape its lobes.
How the system behaves
A roughly 10–15-foot horizontal installation can enhance high-angle regional behavior, while greater safe height can add lower-angle opportunity; neither guarantees a path.
The boundary that prevents mistakes
Match the geometry to the intended stations, use reviewed patterns only for the exact case, log band/time/orientation/height, and compare scheduled regional and longer-path reports.
Use this field sequence
Define the exact configuration and intended path, inspect the complete installation, begin measurements at low power, record the result, and change one variable at a time.
Source boundary
CHA OCF40 User Guide 250513. Use the exact current configuration, components, feed, support, geometry, power, and safety limits; mechanical fit does not establish compatibility.
